Conventionally, a recoil starter is used with a manually started internal combustion engine, such as a small two-stroke engine, for example. A rope pulley is rotated by pulling an attached recoil rope that is wound onto the rope pulley, thereby transmitting a rotational force to a crankshaft of the internal combustion engine by way of a ratchet and/or clutch mechanism between the pulley and a flywheel and crankshaft. Rotation of the crankshaft drives a piston and helps provide fuel for ignition. Rotation of the flywheel causes a magneto to power a spark plug, creating a spark for ignition of the engine fuel.
In operating such a starter mechanism, abrupt changes in the engine torque due to the compression of an air/fuel mixture by the piston and the cylinder within the engine typically result in an uneven and jarring pulling force during starting, and possibly even some kickback forces. These forces can make starting the engine difficult for a user, creating stresses that can even cause an injury.
To reduce these fluctuations in pulling force, starter mechanisms have been provided which include a second rotating member, coupled to the pulley by way of a buffering component, such as a spring, wherein this second rotating member engages with the engine crankshaft, typically using a ratchet mechanism, for transmission of the rotational force. In such a solution, rotational energy stored within the buffering spring component is used to assist in transmitting a rotational force to the engine crankshaft during periods of higher required torque, thereby dampening the pulling force required by the operator and smoothing the starting operation for the user.
Despite this modification, drawbacks in the typical buffered recoil starter system remain. The added components necessary to construct such a system result in added expense of material, additional wear considerations, and more cumbersome assembly procedures. Finally, the delayed acceleration of the rotating crankshaft and flywheel can result in difficult starting when a spark is initially provided for ignition.
Needed is a way to provide a starter device that utilizes a buffering spring to enable starting the engine with a reduced pulling force, while at the same time reducing the inevitable stresses on a spring component to provide greater durability and reliability.
Additionally, it would be beneficial to provide such a buffered starter device that produces a spark properly timed with the more slowly accelerating crankshaft to ease starting. Further benefits would also be realized by incorporating additional improvements in ease of assembly and durability of the bearing surfaces, while minimizing the use of costly materials and extra components.